Inductive wireless-telephone system for railroads and the like.



V. G. WERNER & K. H. WARFVINGE. INDUCTIVE WIRELESS TELEPHONE SYSTEM FOR RAILROADS AND THE LIKE.

APPLICATION FILED AUG.I4, I9I6.

Patented Oct. 9, 1917.

trons.

appearance illustrated in Fig. 1.

VICTOR GABRIEL WERNER AND KARI HJALMAR l/VABFVINGE, ,0 STGCKHOLI'ZI, SWEDEN.

INDUCTIVE WIRELESS-TELEPHONE SYSTEM FOR RAILROADS AND THE LIKE.

Application filed August 14, 1916.

To all whom it may concern:

Be it known that we, Vroron GABRIEL lWERNn-R and KARL HJALMAR WARFVINGE,

in an inductive wireless telephone system for telephoning between moving railroad trains, or other vehicles, or between such and railroad. stations or other stationary places. In the accompanying drawing, Figure 1 represents in a curve, the relation between current and frequency. Fig. 2 is a diagram of the circuits of the apparatus carried on the moving vehicle. 3 is a diagram of another such circuit. The said system consists of an inductive connection between a closed movable induction circuit and a closed stationary induction circuit, the former of which is arranged on the train, and the latter of which is formedby a single or a double aerial conductor along the track, which conductor is connected to a fixed station. The inductive part of the movable circuit preferably consists of an induction frame comprising one or several turns of an insulated conductor and inclosing the greatest possible induction area, or it may consist of several such induction frames.

The purpose of the present invention is to increase the sensitivity and the inductive efi'ect of the movable induction circuit by making-the same as a compound oscillation circuit possessing a plurality of natural oscillation periods of its own. The tuning of the circuit is preferably made so that the frequencies of these natural oscillations are uniformly distributed over the range of frequency of the most important speech oscilla- The intervals between the natural frequencies should not be greater than is necessary from practical reasons with regard to the fact that the arrangement becomes complicated in the same degree as the number of branches of the compound circuit is increased. lhe peaks of the resonance curve should thus be brought to flow together and become leveled as much as possible, so that the curve may obtain about the Specification of Letters Patent.

Patented (lot. 9, Lilli.

Serial no. 114,684.

and 5 denote the frequencies of the natural oscillations; the ordinates are proportional to the induction in the circuit. T he damping of the circuit also contributes to the fiattening of the upper part of the resonance curve. The damping should be elder/ted as much as possible by useful resistance (of the microphone or of the receiver). Under such conditions the tuning has no detrimental effect on the articulation of the speech, but otters a possibility of materially increasing the number of turns of the induction frame without the resistance to alternating current in the induction circuit being increased in a corresponding degree.

Fig. 2 shows an example of a compound oscillatory circuit having five natural oscil lation periods of its own. L is the induction. frame, L one winding of an induction coil, the other winding of which may be connected by means of the switch S either with the microphone M and-its source B of current, or with the receiver H. The tuned branches 1, 2, 3, 4, and 5, each of which includes an inductive reactance L L etc, and a condenser C G etc, or only a condenser G cause in the resonance circuit an equal number of natural oscillations of its own. A change in the self-induction or in the capacity of one branch causes, primarily, a change of the natural oscillation of this branch, but influences also the other branches to some extent.

Fig. 3 shows an embodiment in which one of the natural frequenciespreferably the mean freque of the range of speech oscillations -ma'y be made independent of the other. This is efi'ected by tuning the branch L L C and the branch L C, to the said mean frequency n in such manner that 1 n my (L -L )G -L,C,.

Otherwise the arrangement according to 1 1s ana o ore to la s ow l .1 Fg3 lgitt h ninF g with the difierence only that one of the branches may include an inductive reactance only, without a condenser.

The stationary circuit may also be tuned to the speechoscillations in the same man- The invention may, of course, also be used on vessels, for instance in canal and river traflic. 4

We claim:

In an inductive Wireless telephone system i for railroads, the combination of a stationary circuit consisting of an aerial conductor along the railroad track and connected to a fixed. telephone station, and a circuit on the train comprising a microphone, a receiver,

and a source of electrical energy, said circults belng 1n inductive relation to each circuit to oscillations Within this range, sub- 20 stantially as described.

VICTOR GABRIEL WERNER.

KARL HJALMAR WARFVINGE. 

